William has also started an interesting discussion where he makes an interesting point:

In the case of the Android App Market, paid app sales are a fraction of what one would expect. The top paid apps have sold only a few 1000 copies, free apps have reached download numbers of over 250,000.

Why? Most users have not opted-in to Google Checkout, which is the billing system used.

Apple, of course, requires users to opt into iTunes, but iTunes already has widespread acceptance. 93% of iPhone users have purchased an app.

My understanding is that Google approached T-Mobile about this and the idea of adding carrier billing as an option was rejected.

So let me get this straight:1. Apple cleverly cuts operators out of the app revenue stream.2. Competing 'open' platform, Android appears.3. Operators reject Google's offer to use their billing systems for app purchases.4. Operators see no revenue from app sales on iTunes AND Android App Marketplace.5. Android is a non-starter for app developers in business terms.The question is, will users opt in for PayPal when the RIM App World turns on?